#!/usr/bin/perl
use warnings;
use strict;

use Text::CSV_XS;

my $csv = 'Text::CSV_XS'->new({binary => 1});
open my $CSV, '<', shift or die $!;

while (my $row = $csv->getline($CSV)) {
    $csv->say(\*STDOUT, [ map length ? $_ : 'NULL', @$row ]);
}